1. Field of the Invention
This present invention relates to an antenna device capable of measuring a displacement or inclination of a support structure having influence on the pointing direction to correct the pointing direction.
2. Description of the Related Art
In the field of a radio astronomy, there is a growing demand for observing electric wave of higher frequency from millimeter wave to sub-millimeter wave in recent years. In observing the radio celestial body of higher frequency, it is required that a reflector surface of antenna and a directional tracking of beam have higher precision. On the other hand, to increase the observation efficiency, the antenna having a larger aperture has progressed and it is desired to allow the observations in all kinds of weather at day and night. If the aperture is larger, an own weight deformation of antenna is increased, and a thermal deformation or deformation due to wind pressure is increased, whereby it is difficult to attain a high directional tracking precision. To satisfy a demand for high directional tracking precision, it is required a technique for measuring and correcting the pointing error of a reflector for the antenna in real time. One of the factors of having influence on the pointing error of antenna is a deformation of a structural portion supporting the main reflector, and as means for measuring this deformation, optical instrumentation means using a laser and an optical detector and instrumentation means with a mechanical method may be considered. However, for the former, it is difficult to make the fast measurements because there is a large measurement error due to atmospheric fluctuations within the optical system, and due to a processing delay of optically detected image. On the other hand, the instrumentation means with the mechanical method which obtains a pointing error of an antenna structure by installing a frame structure unsusceptible to thermal deformation or wind deformation in an antenna supporting structure was disclosed in JP-A-2007-129454.